In order to address the issue of power fluctuations and impact currents generated by the energy storage converter during the on-grid and off-grid switching conditions, based on the parallel operation and shared current inner loop of constant power (power quality, PQ) control and virtual synchronous generator (VSG) control, a sliding mode active disturbance rejection control (SM-ADRC) inner loop control strategy was proposed. Firstly, to address the issue of insufficient disturbance estimation capability of the traditional extended state observer (ESO), an error variable reconstruction observer structure was introduced, which optimized the dynamic characteristics of disturbance observation. Secondly, to improve the insufficient robustness of the traditional active disturbance rejection control, the double integral sliding mode control (DISMC) was substituted for the original proportional-derivative (PD) link, and an improved exponential convergence law was designed, aiming to enhance the stability of the control system and effectively weaken the inherent chattering effect of the sliding mode control. Further, based on the Lyapunov theory, the stability of the control was proved. Finally, the results of system simulation experiments show that this method has smaller current impact and better dynamic performance compared to proportional-integral (PI) control and traditional active disturbance rejection control during the switching between grid-connected and off-grid operation, and reduces the harmonic content during grid connection.